Systems of the above-described type are known in which comb filters are used. However, a comb filter only operates exactly when two time sequential lines of the television signal have the same signal content. If the correlation between the signal content of two time sequential lines is poor, parts of the chrominance signals will remain in the luminance signal thereby causing so-called cross-luminance disturbances. DT-OS No. 2,615,023 discloses a system in which a band rejection filter is connected to the output of the comb filter furnishing the luminance signal and the filtering effect is controlled in such a manner that it becomes more and more pronounced the more difference exists in the chrominance information of two time sequential lines. It is, however, very difficult to design and construct the band rejection filter having the required transfer characteristic.